Technical Abstract:
This research was conducted to determine the effect of tillage on distribution of weed seed in the soil, emergence percentage of the seedbank, timing of weed emergence and the growth of emerged weed seedlings. A field study was conducted in established tillage plots at Waseca, MN, in 1993 and 1994. The tillage systems of moldboard plow (MP), chisel plow (CP) and no tillage (NT), had been in place since 1983. The foxtail seedbank in NT was greater than in MP or CP. Eighty-three percent of the foxtail seedbank in NT was concentrated in the 0-1 and 1-3 cm depths. In the CP and MP systems, the foxtail seedbank was more evenly distributed throughout the soil profile. NT resulted in greater foxtail cumulative emergence than MP or CP. Percent emergence of the foxtail seedbank was not different among tillages. Broadleaf cumulative emergence and percent emergence of the seedbank was not different among tillages. To measure the influence of tillage weed growth, three 50-cm diameter rings were established in each plot and the cylindrical volume of each weed species was calculated weekly. NT accumulated foxtail volume at a greater rate than MP or CP, but MP and CP were not different. Foxtail volume 65 days after planting was greater in NT compared to MP or CP, but MP and CP were not different. No difference was detected in broadleaf volume accumulation rate or total broadleaf volume accumulated among tillages. Due to greater seedbank, a higher concentration of weed seed in the upper layers of soil, and the greater rate of foxtail volume accumulation and larger foxtail volume accumulation as compared to MP or CP systems, foxtails could become a major weed problem in reduced tillage systems.